Processes are known for the treatment of minerals containing one or two metals of particular interest for removal of the metal(s). These processes become extremely costly and complex to operate when treating minerals having complex compositions. Furthermore the attaining of product purity is also more difficult when the mineral has a complex composition or contains many contaminants.
A major problem today (and in the future) relates to the disposal of waste and by-products resulting from the existing treatment of minerals for metal recovery. For sulfur containing minerals, this problem is exacerbated in that a typical by-product is sulfur either in the form of sulfur dioxide gas or sulfuric acid. Enormous atmospheric emission problems stem from the production of sulfur dioxide (including acid rain) and it has been usual to reclaim sulfur dioxide by producing sulfuric acid. However, sulfuric acid is so prevalent that many producers have actually been required to incur cost for its removal from site.
Given the problems of the high level of waste and by-products from the treatment of minerals, and more particularly to the by-production of sulfur dioxide/sulfuric acid, attempts have been made to develop processes wherein the disposal and/or reclaiming of by-products is simplified.
U.S. Pat. No. 3,673,061 to Cyprus Metallurgical Process Corporation describes the oxidation of copper sulfides in a slurry at the anode of an electro-chemical cell, with the requirement for an anode current density of at least 12 amps per square foot for decomposition of the copper sulfide. The presence of iron in many minerals results in a low anode current efficiency for copper in this process due to power consumed by iron oxidation. The electrolytic production of iron in this process is very expensive and renders the process uneconomic both in terms of efficiency and overall cost.
Australian patent application number 46913/72 to the Duval Corporation describes a process involving the ferric chloride and cupric chloride leaching of copper sulfide ores. The process is quite complex and requires temperatures of around 140.degree. C., and pure oxygen at pressures of up to 3.5 atmospheres.
U.S. Pat. No. 4,061,552 to Dextec Metallurgical Pty Ltd overcomes the disadvantages of relatively high operating temperatures and pressures by electrolysing copper sulfides in the anode compartment of an electrolytic cell, with the simultaneous addition of air to precipitate iron. However, it is difficult to produce a pure product from the Dextec process.
Another existing process is the Cuprex Process. The Cuprex process involves leaching a copper concentrate with ferric chloride solution, solvent extraction of the ferric chloride solution, scrubbing, stripping and then electrolysis to produce copper. The Cuprex process is an expensive process, having a high power consumption, high capital and operating costs and is overall a complex procedure to operate. Furthermore, products such as gold must be removed using existing methods which have undesirable side effects.
It would be advantageous if at least preferred forms of the present invention ameliorated the deficiencies of the prior art or, at the very least, provided an effective alternative to prior art processes.